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A new type of charged defect in amorphous chalcogenides

S. I. Simdyankin·T. A. Niehaus·G. Natarajan·Th. Frauenheim·S. R. Elliott
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Abstract

We report on density-functional-based tight-binding (DFTB) simulations of a series of amorphous arsenic sulfide models. In addition to the charged coordination defects previously proposed to exist in chalcogenide glasses, a novel defect pair, [As4]--[S3]+, consisting of a four-fold coordinated arsenic site in a seesaw configuration and a three-fold coordinated sulfur site in a planar trigonal configuration, was found in several models. The valence-alternation pairs S3+-S1- are converted into [As4]--[S3]+ pairs under HOMO-to-LUMO electronic excitation. This structural transformation is accompanied by a decrease in the size of the HOMO-LUMO band gap, which suggests that such transformations could contribute to photo-darkening in these materials.

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S. I. Simdyankin, T. A. Niehaus, G. Natarajan, Th. Frauenheim, S. R. Elliott. 2004-09-17. A new type of charged defect in amorphous chalcogenides. https://doi.org/10.1103/physrevlett.94.086401

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